1. Field of the Invention
The invention relates to a door closer having a cam drive, and in particular a door closer having a clearance-free piston assembly.
2. Description of Prior Art
In the state of the art, a differentiation is made between door closers and door drives. In the case of door closers, the door has to be opened manually by a person. During the opening process, energy is stored, e.g. in a closer spring, and the door closer is able to close the door using the stored energy. Contrary thereto, the door drive is an assembly that automatically opens and closes the door by an additional auxiliary energy, e.g. by a motor or hydraulics . In particular when considering the hydraulic circuits in door drives and door closers, significant differences can be found. In electro-mechanic door drives, a motor and a pump are always, provided, which apply the required hydraulic pressure. The respective pressure chambers are thereby actively charged with hydraulic pressure, such that the opening of the door is effected. Thus, in the door drive, the pressure is generated by the internal components, i.e. motor and pump. Contrary thereto, the pressure chambers in a door closer are filled by expansion of the chambers and by suctioning the hydraulic oil from other spaces of the door closer. Herein, the energy for the closer spring and for the pressure generation is supplied to the door closer by opening the door. Consequently, the force and moment characteristics as well as the occurring loads are mostly different for a door closer and a door drive. The door drive has to apply the energy for accelerating the door in an opening direction additionally, whereas, in case of the door closer, the door is accelerated in an opening direction by the user.